Magento: How to remove discount coupon code?

Magento offers a built in coupon code feature to provide shopping cart customers with discounts when shopping on their ecommerce website. You can post discount codes in emails, blogs and social networks to generate more traffic and entice paying customers to your ecommerce website. But often, website owners don’t want to offer discount codes on their shopping cart. Fortunately for ecommerce web designers, it is quite easy to disable the discount coupon code function on a Magento shopping cart website.
Edit your checkout.xml layout file. The default file in Magento 1.6 would be located in app/design/frontend/base/default/layout/checkout.xml